Adds to Melange a tags framework based on taggable-mixin.
The taggable-mixin allowed only tag per Datastore model. This is extended
framework allows any arbitrary number of tags per Datastore model. Also,
now one can define different models for different Tag types which are all
inherited from the base Tag model provided by taggable-mixin.
The GHOPTask model makes use of 2 tags per model, one for difficulty and the
other for task_type, both using the tags framework.
Reviewed by: Paweł Sołyga
"""
Useful auxilliary data structures for query construction. Not useful outside
the SQL domain.
"""
class EmptyResultSet(Exception):
pass
class FullResultSet(Exception):
pass
class MultiJoin(Exception):
"""
Used by join construction code to indicate the point at which a
multi-valued join was attempted (if the caller wants to treat that
exceptionally).
"""
def __init__(self, level):
self.level = level
class Empty(object):
pass
class RawValue(object):
def __init__(self, value):
self.value = value
class Aggregate(object):
"""
Base class for all aggregate-related classes (min, max, avg, count, sum).
"""
def relabel_aliases(self, change_map):
"""
Relabel the column alias, if necessary. Must be implemented by
subclasses.
"""
raise NotImplementedError
def as_sql(self, quote_func=None):
"""
Returns the SQL string fragment for this object.
The quote_func function is used to quote the column components. If
None, it defaults to doing nothing.
Must be implemented by subclasses.
"""
raise NotImplementedError
class Count(Aggregate):
"""
Perform a count on the given column.
"""
def __init__(self, col='*', distinct=False):
"""
Set the column to count on (defaults to '*') and set whether the count
should be distinct or not.
"""
self.col = col
self.distinct = distinct
def relabel_aliases(self, change_map):
c = self.col
if isinstance(c, (list, tuple)):
self.col = (change_map.get(c[0], c[0]), c[1])
def as_sql(self, quote_func=None):
if not quote_func:
quote_func = lambda x: x
if isinstance(self.col, (list, tuple)):
col = ('%s.%s' % tuple([quote_func(c) for c in self.col]))
elif hasattr(self.col, 'as_sql'):
col = self.col.as_sql(quote_func)
else:
col = self.col
if self.distinct:
return 'COUNT(DISTINCT %s)' % col
else:
return 'COUNT(%s)' % col
class Date(object):
"""
Add a date selection column.
"""
def __init__(self, col, lookup_type, date_sql_func):
self.col = col
self.lookup_type = lookup_type
self.date_sql_func = date_sql_func
def relabel_aliases(self, change_map):
c = self.col
if isinstance(c, (list, tuple)):
self.col = (change_map.get(c[0], c[0]), c[1])
def as_sql(self, quote_func=None):
if not quote_func:
quote_func = lambda x: x
if isinstance(self.col, (list, tuple)):
col = '%s.%s' % tuple([quote_func(c) for c in self.col])
else:
col = self.col
return self.date_sql_func(self.lookup_type, col)